Drug-resistant Plasmodium Research Articles

Setting Up an NGS Sequencing Platform and Monitoring Molecular Markers of Anti-Malarial Drug Resistance in Djibouti

Djibouti is confronted with malaria resurgence, with malaria having been occurring in epidemic proportions since a decade ago. The current epidemiology of drug-resistant Plasmodium falciparum is not well known. Molecular markers were analyzed by targeted sequencing in 79 P. falciparum clinical isolates collected in Djibouti city in 2023 using the Miseq Illumina platform newly installed in the country. The objective of the study was to analyze the key codons in these molecular markers associated with antimalarial drug resistance. The prevalence of the mutant Pfcrt CVIET haplotype (92%) associated with chloroquine resistance and mutant Pfdhps-Pfdhfr haplotypes (7.4% SGEA and 53.5% IRN, respectively) associated with sulfadoxine-pyrimethamine resistance was high. By contrast, Pfmdr1 haplotypes associated with amodiaquine (YYY) or lumefantrine (NFD) resistance were not observed in any of the isolates. Although the “Asian-type” PfK13 mutations associated with artemisinin resistance were not observed, the “African-type” PfK13 substitution, R622I, was found in a single isolate (1.4%) for the first time in Djibouti. Our genotyping data suggest that most Djiboutian P. falciparum isolates are resistant to chloroquine and sulfadoxine-pyrimethamine but are sensitive to amodiaquine, lumefantrine, and artemisinin. Nonetheless, the presence of an isolate with the R622I PfK13 substitution is a warning signal that calls for a regular surveillance of molecular markers of antimalarial drug resistance.

Ultrasound-assisted synthesis and structure elucidation of novel quinoline-pyrazolo[1,5-a]pyrimidine hybrids for anti-malarial potential against drug-sensitive and drug-resistant malaria parasites and molecular docking

Ultrasound-assisted synthesis and structure elucidation of novel quinoline-pyrazolo[1,5-a]pyrimidine hybrids for anti-malarial potential against drug-sensitive and drug-resistant malaria parasites and molecular docking

Towards next-generation treatment options to combat Plasmodium falciparum malaria.

Malaria, which is caused by infection of red blood cells with Plasmodium parasites, can be fatal in non-immune individuals if left untreated. The recent approval of the pre-erythrocytic vaccines RTS, S/AS01 and R21/Matrix-M has ushered in hope of substantial reductions in mortality rates, especially when combined with other existing interventions. However, the efficacy of these vaccines is partial, and chemotherapy remains central to malaria treatment and control. For many antimalarial drugs, clinical efficacy has been compromised by the emergence of drug-resistant Plasmodium falciparum strains. Therefore, there is an urgent need for new antimalarial medicines to complement the existing first-line artemisinin-based combination therapies. In this Review, we discuss various opportunities to expand the present malaria treatment space, appraise the current antimalarial drug development pipeline and highlight examples of promising targets. We also discuss other approaches to circumvent antimalarial resistance and how potency against drug-resistant parasites could be retained.

“Novel chemo-enzymatic synthesis, structural elucidation and first antiprotozoal activity profiling of the atropoisomeric dimers of trans-8-Hydroxycalamenene”

Leishmaniasis and malaria are two debilitating protozoan diseases affecting millions globally, particularly in tropical and subtropical regions. Current therapeutic options face significant challenges due to emerging drug-resistant strains, necessitating the discovery of novel antiprotozoal agents. This study explores, for the first time, the antiprotozoal potential of calamenenes and their dimers, naturally occurring sesquiterpenes found in essential oils, through a novel chemo-enzymatic synthesis approach. Using the laccase from Trametes versicolor, atropoisomeric dimers of (−)- and (+)-8-trans-hydroxycalamenene were synthesized from commercially available (−)- and (+)-menthol. Structural elucidation was achieved via 2D-NMR spectroscopy, electronic circular dichroism, and DFT calculations. In vitro profiling against Leishmania spp and drug-resistant Plasmodium falciparum revealed that calamenene dimers exhibited significantly higher antiprotozoal activity compared to their monomeric counterparts, highlighting the potential of dimeric terpenoids as promising antiprotozoal agents. This work lays the foundation for developing novel antimalarial drugs based on calamenene scaffolds, encouraging further interactome studies to optimize their pharmacological properties.

<i>In-Silico</i> Screening of Prenylated Quercetin from <i>Globimetula oreophila</i> Against <i>Plasmodium falciparum</i> Enzymes: Hope for New Antimalarial Drugs

Malaria continues to be one of the most devastating global health problems due to the high morbidity and mortality it causes in endemic regions. The search for new antimalarial targets is vital because of the increasing prevalence of drug resistance in malaria parasites. Malarial proteases constitute promising therapeutic targets as they play important roles in the parasite life cycle. The inhibition of these enzymes has pharmacological and therapeutic significance since they are involved in numerous processes, including the development, invasion, egress, and breakdown of host hemoglobin to release amino acids for parasite sustenance. In this study, <i>in silico</i> techniques were used to shed light on the mechanisms underlying the inhibitory effects of prenylated quercetin isolated from <i>Globimetula oreophila</i> on plasmepsin I and II, falciparum 2 and 3, <i>Plasmodium falciparum</i> calcium-dependent protein kinase 2, dihydrofolate reductase-thymidylate synthase, and serine repeat antigen 5. The test compound significantly interacts with key enzyme binding pockets through hydrogen bonds, van der Waals, and hydrophobic interactions, influencing protease specificity control. Crucial ligand features like carbonyl and hydroxyl groups were identified as essential for receptor interactions. Comparative analysis revealed the test compound's strong binding affinities with energies ranging from -6.4 Kcal/mol to -9.4 Kcal/mol, indicating competitive potential against various enzymes, particularly excelling against <i>Pf</i>DHFR-TS, plasmepsin-I, and SERA5 compared to native ligands. This suggests the compound's ability to competitively inhibit enzyme activity by targeting co-factor binding sites, especially with specific proteases, holding promise for therapeutic applications as potent inhibitors for the prevention and treatment of malaria.

A kalihinol analog disrupts apicoplast function and vesicular trafficking in P. falciparum malaria.

We report the discovery of MED6-189, an analog of the kalihinol family of isocyanoterpene natural products that is effective against drug-sensitive and drug-resistant Plasmodium falciparum strains, blocking both asexual replication and sexual differentiation. In vivo studies using a humanized mouse model of malaria confirm strong efficacy of the compound in animals with no apparent hemolytic activity or toxicity. Complementary chemical, molecular, and genomics analyses revealed that MED6-189 targets the parasite apicoplast and acts by inhibiting lipid biogenesis and cellular trafficking. Genetic analyses revealed that a mutation in PfSec13, which encodes a component of the parasite secretory machinery, reduced susceptibility to the drug. Its high potency, excellent therapeutic profile, and distinctive mode of action make MED6-189 an excellent addition to the antimalarial drug pipeline.

A novel peptide pair-based rapid fluorescent diagnostic system for malaria Plasmodium falciparum detection

Advanced diagnostic materials, such as aptamers, are required due to the scarcity of efficient diagnostic antibodies and the low sensitivity of rapid diagnostic kits at detecting the malaria parasite, Plasmodium falciparum. MethodsTwo peptides M2.9 [(KPTAEQTESPELQSAPEN) and M2.17 (KILFNVYSPLGCTCECWV)] were designed using simple epitope prediction tools and modified against the merozoite surface antigen 2 of P. falciparum (Pf.MSP2) by 3-dimensional modeling based on binding affinity. Based on five prediction tools for hydropathy, M2.17 was selected as an appropriate capture peptide. A peptide-based fluorescence-linked immunosorbent assay (FLISA) and a peptide pair-based fluorescent immunochromatographic test strip (FICT) were developed to detect P. falciparum 3D7 (drug-sensitive) and P. falciparum K1 (multi drugs-resistant) strains. ResultsBioinformatic analysis of two peptides demonstrated the potential binding affinity with the merozoite surface protein 2 of P. falciparum (Pf.MSP2) with a positive hydropathy value. The limit of detection (LOD) of FLISA was 10 parasites/μL and of a peptide pair-linked rapid FICT system was 5 and 200 parasites/μL for P. falciparum 3D7 and K1, respectively. Compared to commercial rapid detection systems (RDTs), a peptide pair-linked FICT system exhibited a 20-fold greater efficiency in detecting P. falciparum 3D7 and specifically discriminated another protozoan spp. ConclusionA peptide pair-linked rapid diagnostic strip could be an alternative to conventional RDTs for monitoring wild-type and drug-resistant malaria parasites.

Challenges in Malaria Control and Prevention in East Africa

Malaria remains a critical public health issue in East Africa, where high transmission rates persist despite extensive control and prevention efforts. This review article explores the multifaceted challenges that hinder effective malaria control and prevention in the region, including the emergence of drug-resistant Plasmodium parasites, insecticide-resistant mosquito vectors, inadequate healthcare infrastructure, socio-economic barriers, and environmental factors. The review methodology involved analyzing recent studies, reports, and data from international health organizations. Drug resistance and vector control are significant issues, with resistance to both anti-malarial drugs and insecticides compromising treatment efficacy and prevention efforts. Additionally, socio-economic factors such as poverty and lack of education, coupled with climate variability and environmental changes, further complicate malaria control. Addressing these challenges requires a coordinated approach that integrates continuous monitoring, healthcare system strengthening, community engagement, and international collaboration. By tackling these issues, East Africa can improve its malaria control efforts and ultimately enhance the health outcomes of its populations. Keywords: Malaria Control, Drug Resistance, Insecticide Resistance, Healthcare Infrastructure, Socio-Economic Barriers.

Naringin and chloroquine combination mitigates chloroquine-resistant parasite-induced malaria pathogenesis by attenuating the inflammatory response

BackgroundMalaria, characterised by inflammation and multi-organ complications, needs novel chemotherapeutics due to the rise of drug-resistant malaria parasites, which is a serious health issue. Naringin (NGN), a flavanone glycoside (naringenin 7-O-neohesperidose), has a broad spectrum of pharmacological activities but its effect against malaria, alone and in combination, was not deeply investigated. PurposeTo assess the pharmacological efficacy of NGN alone and in combination with chloroquine (CQ) against a Plasmodium strain resistant to CQ and to elucidate its potential mode of action. MethodsThe anti-inflammatory potential of NGN was assessed in mouse microglial cells stimulated with hemozoin by analyzing inflammatory cytokines production. The anti-plasmodial potential of NGN was subsequently tested alone and in combination with CQ against the K1 strain of Plasmodium using the fixed ratio combination method. Further, we evaluated NGN's antimalarial efficacy against the CQ-resistant Plasmodium yoelii nigeriensis N67 strain (P. yoelii), both alone and in combination with CQ, by measuring parasitemia and survival rates. To comprehend the impact of NGN on malaria-induced inflammation in mice, we measured pro-inflammatory cytokines elevated by activated NF-кB signalling. These findings were supported by mRNA and immunohistochemical analyses of malaria-infected mice's liver and brain tissues. ResultsOur study demonstrated that NGN displayed anti-plasmodial activity, which was further augmented when combined with CQ. At 50 µM, NGN significantly reduced the elevation of pro-inflammatory cytokines in synthetic hemozoin-stimulated microglial cells. Compared to P. yoelii-infected mice, NGN (12.5 mg kg-1) significantly reduced parasitemia in mice, resulting in a survival period of up to 13 days. Survival improved by up to 20 days when NGN and CQ were given in combination. NGN, as revealed by immunohistochemical examination of brain and liver tissues, interfered with the NF-кB pathway, potentially reducing the elevation of pro-inflammatory cytokines (TNF-α, IL-1β, IL-18, IFN-γ, and IL-6). This was supported by the overexpression of inflammation-regulatory genes (TGFβ, Nrf2, HO-1, and iNOS) and the downregulation of inflammation-stimulating genes (NF-κB, NLRP3, and caspase-1). Histopathological analysis demonstrated the potential of NGN to restore liver and brain tissues to normal. The substantial decrease in the expression and production of ICAM-1 protein in the brain tissue implies the beneficial effects of NGN, pointing towards its potential for mitigating brain pathology. ConclusionThe findings of this study revealed NGN as a promising drug-like candidate for the management of CQ-resistant parasite-induced malaria pathogenesis for adjunctive therapy in combination with standard antimalarial drugs through its modulation of the NF-κB-mediated inflammation.

Antiplasmodial action of 4-nitrobenzenesulfonamide chalcones: Design, synthesis, characterisation, in vitro and in silico evaluation against blood stages of Plasmodium falciparum 3D7.

Malaria is an intracellular protozoan parasitic disease caused by Plasmodium species with significant morbidity and mortality in endemic regions. The complex lifecycle of the parasite and the emergence of drug-resistant Plasmodium falciparum have hampered the efficacy of current anti-malarial agents. To circumvent this situation, the present study attempts to demonstrate the blood-stage anti-plasmodial action of 26 hybrid compounds containing the three privileged bioactive scaffolds (sulfonamide, chalcone, and nitro group) with synergistic and multitarget action. These three parent scaffolds exhibit divergent activities, such as antibacterial, anti-malarial, anti-fungal, anti-inflammatory, and anticancer. All the synthesised compounds were characterised using various spectroscopic techniques. The in vitro blood-stage inhibitory activity of 26 hybrid compounds was evaluated against mixed-stage culture (asynchronize) of human malarial parasite P. falciparum, Pf 3D7 at different concentrations ranging from 25.0 µg/mL to 0.78 µg/mL using SYBR 1 green assay, with IC50 values determined after 48 h of treatment based on the drug-response curves. Two potent compounds (11 and 10), with 2-Br and 2,6-diCl substitutions, showed pronounced activity with IC50 values of 5.4 µg/mL and 5.6 µg/mL, whereas others displayed varied activity with IC50 values ranging from 7.0 µg/mL to 22.0 µg/mL. Both 11 and 10 showed greater susceptibility towards mature-stage trophozoites than ring-stage parasites. The hemolytic and in vitro cytotoxicity assays revealed that compounds 11 and 10 did not cause any toxic effects on host red blood cells (uninfected), human-derived Mo7e cells, and murine-derived BA/F3 cells. The in vitro observations are consistent with the in silico studies using P. falciparum-dihydrofolate reductase, where 11 and 10 showed a binding affinity of -10.4 Kcal/mol. This is the first report of the hybrid scaffold, 4-nitrobenzenesulfonamide chalcones, demonstrating its potential as an anti-plasmodial agent.

Drugs resistance and new strategies of prevention against Malaria: An ongoing battle.

From ancient times until 21st century, Malaria has remained a fatal disease. It causes death in many poor and developing countries. Excluding vector control, Antimalarial drugs are the most reliable and effective weapon to tackle this severe disease. The emergence of antimalarial drug resistance in Plasmodium spp. becomes a barrier in Malaria elimination program as there has been no effective antimalarial vaccine till today. Apart from artemisinin, most of the antimalarial drugs have become resistant against malaria at present. Although, reduced efficacy of artemisinin-based combination therapy (ACT) has also been reported from southeast regions of Asia. Mutation of some genes within the parasite play a vital role in this drug resistance. Therefore, malaria is still a prime threat to human death and an unsolved problem. Newly emerging approaches like, vaccine development, plants based antimalarial drugs, nanoparticles, next generation antimalarial drugs should be taken & supported. In addition to that, public awareness is much needed for understanding the fatality of the disease and for encouraging self-protection and early treatment.

Antimalarial activity of cecropin antimicrobial peptides derived from Anopheles mosquitoes.

The emergence of clinically drug-resistant malaria parasites requires the urgent development of new drugs. Mosquitoes are vectors of multiple pathogens and have developed resistance mechanisms against them, which often involve antimicrobial peptides (AMPs). An-cecB is an AMP of the malaria-transmitting mosquito genus Anopheles, and we herein report its antimalarial activity against Plasmodium falciparum 3D7, the artemisinin-resistant strain 803, and the chloroquine-resistant strain Dd2 in vitro. We also demonstrate its anti-parasite activity in vivo, using the rodent malaria parasite Plasmodium berghei (ANKA). We show that An-cecB displays potent antimalarial activity and that its mechanism of action may occur through direct killing of the parasite or through interaction with infected red blood cell membranes. Unfortunately, An-cecB was found to be cytotoxic to mammalian cells and had poor antimalarial activity in vivo. However, its truncated peptide An-cecB-1 retained most of its antimalarial activity and avoided its cytotoxicity in vitro. An-cecB-1 also showed better antimalarial activity in vivo. Mosquito-derived AMPs may provide new ideas for the development of antimalarial drugs against drug-resistant parasites, and An-cecB has potential use as a template for antimalarial peptides.

Characterization of antimalarial activity of artemisinin-based hybrid drugs.

In response to the spread of artemisinin (ART) resistance, ART-based hybrid drugs were developed, and their activity profile was characterized against drug-sensitive and drug-resistant Plasmodium falciparum parasites. Two hybrids were found to display parasite growth reduction, stage-specificity, speed of activity, additivity of activity in drug combinations, and stability in hepatic microsomes of similar levels to those displayed by dihydroartemisinin (DHA). Conversely, the rate of chemical homolysis of the peroxide bonds is slower in hybrids than in DHA. From a mechanistic perspective, heme plays a central role in the chemical homolysis of peroxide, inhibiting heme detoxification and disrupting parasite heme redox homeostasis. The hybrid exhibiting slow homolysis of peroxide bonds was more potent in reducing the viability of ART-resistant parasites in a ring-stage survival assay than the hybrid exhibiting fast homolysis. However, both hybrids showed limited activity against ART-induced quiescent parasites in the quiescent-stage survival assay. Our findings are consistent with previous results showing that slow homolysis of peroxide-containing drugs may retain activity against proliferating ART-resistant parasites. However, our data suggest that this property does not overcome the limited activity of peroxides in killing non-proliferating parasites in a quiescent state.

Quest for malaria management using natural remedies.

Malaria, transmitted through the bite of a Plasmodium-infected Anopheles mosquito, remains a significant global health concern. This review examines the complex life cycle of Plasmodium, emphasizing the role of humans and mosquitoes in its transmission and proliferation. Malarial parasites are transmitted as sporozoites to the human body by biting an infected female Anopheles mosquito. These sporozoites then invade liver cells, multiply, and release merozoites, which infect red blood cells, perpetuating the cycle. As this cycle continues, the affected person starts experiencing the clinical symptoms of the disease. The current treatments for malaria, including chloroquine, artemisinin-based combination therapy, and quinine, are discussed alongside the challenges of drug resistance and misdiagnosis. Although efforts have been made to develop a malarial vaccine, they have so far been unsuccessful. Additionally, the review explores the potential of medicinal plants as remedies for malaria, highlighting the efficacy of compounds derived from Artemisia annua, Cinchona species, and Helianthus annuus L., as well as exploration of plants and phytocompounds like cryptolepine, and isoliquiritigenin against drug-resistant Plasmodium species. Moreover, studies from Pakistan further highlight the diverse vegetal resources utilized in malaria treatment, emphasizing the need for further research into natural remedies. Despite the advantages of herbal medicines, including cost-effectiveness, and fewer side effects; their limitations must be taken into account, including variations in potency and potential drug interactions. The review concludes by advocating for a balanced approach to malaria treatment and prevention, emphasizing the importance of early detection, accurate diagnosis, and integrated efforts to combat the disease in the endemic regions.

The human malaria-Aotus monkey model: a historical perspective in antimalarial chemotherapy research at the Gorgas Memorial Laboratory-Panama.

The human malaria-Aotus monkey model has served the malaria research community since its inception in 1966 at the Gorgas Memorial Laboratory (GML) in Panama. Spanning over five decades, this model has been instrumental in evaluating the in vivo efficacy and pharmacokinetics of a wide array of candidate antimalarial drugs, whether used singly or in combination. The animal model could be infected with drug-resistant and susceptible Plasmodium falciparum and Plasmodium vivax strains that follow a characteristic and reproducible course of infection, remarkably like human untreated and treated infections. Over the years, the model has enabled the evaluation of several synthetic and semisynthetic endoperoxides, for instance, artelinic acid, artesunate, artemether, arteether, and artemisone. These compounds have been evaluated alone and in combination with long-acting partner drugs, commonly referred to as artemisinin-based combination therapies, which are recommended as first-line treatment against uncomplicated malaria. Further, the model has also supported the evaluation of the primaquine analog tafenoquine against blood stages of P. vivax, contributing to its progression to clinical trials and eventual approval. Besides, the P. falciparum/Aotus model at GML has also played a pivotal role in exploring the biology, immunology, and pathogenesis of malaria and in the characterization of drug-resistant P. falciparum and P. vivax strains. This minireview offers a historical overview of the most significant contributions made by the Panamanian owl monkey (Aotus lemurinus lemurinus) to malaria chemotherapy research.

Additive Effect of Some Medicinal Plants Extracts Used for the Treatment of Malaria in Sokoto Metropolis, Nigeria

Malaria remains a threat and exert economic and social burdens in most communities in Africa. Medicinal plants have played an important role in the treatment of malaria worldwide. Several studies have shown that, the efficacies of most antimalarial agents are compromised by the emergence of drug-resistant Plasmodium species. This research was aimed at evaluating the synergistic effect of some medicinal plants used for the treatment of malaria in Sokoto metropolis, Nigeria. Three (3) plants samples were collected and used for the study. They include Azadirachta indica, Carica papaya and Psidium guajava leaves. They were dried and extracted using 50% methanol. Qualitative phytochemical analysis of three (3) plant extracts was carried out using standard methods. The individual extracts and their combinations were subjected to in vivo antiplasmodial activity. Synergistic effect was determined by checkboard method. Phytochemical screening of Azadirachta indica, Carica papaya and Psidium guajava leaves methanol extracts all revealed the presence of phenols, tannins and glycosides in all the extracts. Extract combination of Carica papaya and Psidium guajava demostrated 100% reduction of parasitemia at both 100 and 200 mg/kg b. wt respectively after 72-hour treatment. Determination of synergistic activity showed that Fractional Activity Index (FAI) of Carica papaya and Psidium guajava is greater than 1.0, hence the effect was considered to be additive. The findings of this study had provided scientific bases supporting the traditional use of the plants for the treatment of malaria.

A Mathematical Analysis of Competitive Dynamics and Aggressive Treatment in the Evolution of Drug Resistance in Malaria Parasites

Experimental evidence supports the counterintuitive notion that rapid eradication of pathogens within a host, infected with both drug-sensitive and -resistant malaria parasites, can actually accelerate the evolution of drug-resistant pathogens. This study aims to analyze the competitive dynamics between these two strains through a mathematical model and evaluate the impact of aggressive treatment on the spread of drug resistance. We conducted equilibrium, uncertainty, and sensitivity analyses to assess the model, identifying and measuring the influence of key factors on the outcome variable (the population of drug-resistant parasites). Both equilibrium and local sensitivity analyses concurred that the density of drug-resistant parasites is notably affected by genetic instability, the production rate of red blood cells, the number of merozoites, and competition factors. Conversely, there is a negative relationship between genetic instability and one of the competition coefficients. Global sensitivity analysis offers a comprehensive examination of the impact of each input parameter on the temporal propagation of drug resistance, effectively accounting for the interplay among parameters. Both local and global sensitivity analyses underscore the continuous impact of drug treatment on the progression of drug resistance over time. This paper anticipates exploring the underlying mechanisms of drug resistance and providing theoretical support for developing more effective drug treatment strategies.

Evaluation of the antiplasmodial efficacy of synthetic 2,5-diphenyloxazole analogs of compounds naturally derived from Oxytropis lanata

The persistent prevalence and dissemination of drug-resistant malaria parasites continue to challenge the progress of malaria eradication efforts. As a result, there is an urgent need to search for and develop innovative therapies. In this study, we screened synthetic 2,5-diphenyloxazole analogs from Oxytropis lanata. Among 48 compounds, 14 potently inhibited the proliferation of P. falciparum strains 3D7 (chloroquine-sensitive) and K1 (multidrug-resistant) in vitro, exhibited IC50 values from 3.38 to 12.65 μM and 1.27–6.19 μM, respectively, and were toxic to human foreskin fibroblasts at 39.53–336.35 μM. Notably, Compounds 31 (2-(2′,3′-dimethoxyphenyl)-5-(2″-hydroxyphenyl)oxazole) and 32 (2-(2′,3′-dimethoxyphenyl)-5-(2″-benzyloxyphenyl)oxazole) exhibited the highest selectivity indices (SIs) against both P. falciparum strains (3D7/K1), with values > 40.20/>126.58 and > 41.27/> 59.06, respectively. In the IC50 speed and stage-specific assays, Compounds 31 and 32 showed slow action, along with distinct effects on the ring and trophozoite stages. Microscopy observations further revealed that both compounds impact the development and delay the progression of the trophozoite and schizont stages in P. falciparum 3D7, especially at concentrations 100 times their IC50 values. In a 72-h in vitro exposure experiment at their respective IC80 in P. falciparum 3D7, significant alterations in parasitemia levels were observed compared to the untreated group. In Compound 31-treated cultures, parasites shrank and were unable to reinvade red blood cells (RBCs) during an extended 144-h incubation period, even after compound removal from the culture. In vivo assessments were conducted on P. yoelii 17XNL-infected mice treated with Compounds 31 and 32 at 20 mg/kg administered once daily for ten days. The treated groups showed statistically significant lower peaks of parasitemia (Compound 31-treated: trial 1 12.7%, trial 2 15.8%; Compound 32-treated: trial 1 12.7%, trial 2 14.0%) compared to the untreated group (trial 1 21.7%, trial 2 28.3%). These results emphasize the potential of further developing 2,5-diphenyloxazoles as promising antimalarial agents.

Investigating the impact of solvation on p-Phenylenediamine - 2-Amino pyrimidine - Formaldehyde Terpolymer (P2APF) ligand's reactivity and drug suitability for malaria treatment: Insights from experimental and quantum calculations

This study aims at investigating the drug potential of p-Phenylenediamine – 2-Amino Pyrimidine – Formaldehyde terpolymer (P2APF) ligand against drug resistant Plasmodium falciparum. Plasmodium falciparum, an embodiment of cunning among malaria parasites, thrives in regions plagued by rampant mosquito transmission, subpar vector control, and limited access to effective treatments. To this end, this study explored the structural properties of the p-Phenylenediamine – 2-Amino Pyrimidine – Formaldehyde terpolymer (P2APF) ligand, (comprising p-Phenylenediamine, 2-Aminopyrimidine, and Formaldehyde) as a drug potent ligand against the common proteins coding for malaria infection. Various spectroscopic techniques such as FT-IR, UV–visible, and NMR (1H & 13C) spectroscopy were employed both experimentally and theoretically. Additionally, the ligand's surface morphology was investigated using scanning electron microscopy. To comprehend the influence of solvation, theoretical investigations utilizing density functional theory (DFT) at the B3LYPD(BJ)/6-311G++G (2d,2p) level were conducted in DMSO, water, and methanol solvents. The results from the frontier molecular orbital (FMO) analysis provided valuable insights into the electronic properties and solvation effects of P2APF. Specifically, the calculated energy gap of 3.671 eV for P2APF_methanol and 3.672 eV for P2APF_DMSO suggested these solvents as promising environments for reactivity and interactions. Molecular docking studies unveiled the most notable binding affinity between P2APF and the 5UMB chaperone protein receptor, exhibiting a binding affinity of -7.3 kcal/mol on serine and aspartic acid residues, with an average bond distance of 2.25 Å. This robust protein-ligand interaction signifies the promising potential of the P2APF ligand in targeting this specific receptor, thereby combating drug-resistant strains of Plasmodium falciparum for the present and the future.

Hybrid Peptide-Alkoxyamine Drugs: A Strategy for the Development of a New Family of Antiplasmodial Drugs.

The emergence and spread of drug-resistant Plasmodium falciparum parasites shed a serious concern on the worldwide control of malaria, the most important tropical disease in terms of mortality and morbidity. This situation has led us to consider the use of peptide-alkoxyamine derivatives as new antiplasmodial prodrugs that could potentially be efficient in the fight against resistant malaria parasites. Indeed, the peptide tag of the prodrug has been designed to be hydrolysed by parasite digestive proteases to afford highly labile alkoxyamines drugs, which spontaneously and instantaneously homolyse into two free radicals, one of which is expected to be active against P. falciparum. Since the parasite enzymes should trigger the production of the active drug in the parasite's food vacuoles, our approach is summarized as "to dig its grave with its fork". However, despite promising sub-micromolar IC50 values in the classical chemosensitivity assay, more in-depth tests evidenced that the anti-parasite activity of these compounds could be due to their cytostatic activity rather than a truly anti-parasitic profile, demonstrating that the antiplasmodial activity cannot be based only on measuring antiproliferative activity. It is therefore imperative to distinguish, with appropriate tests, a genuinely parasiticidal activity from a cytostatic activity.